Various types of semiconductor photodetectors such as photodiodes are widely used in different light sensing applications, for example, in imaging and non-imaging light sensing systems for medical, security, and industrial applications as well as in solar cells.
Typically, a semiconductor photodetector comprises a photodiode based on a p-n junction. A p-n junction is commonly formed by implanting foreign impurities on a semiconductor substrate surface, i.e. impurities of different conductivity type than the semiconductor substrate, and annealing the implanted region. Oxide may then be grown for passivation purposes on the surface of the structure comprising the p-n junction. Contacts may be formed to the semiconductor regions with different conductivity types, for example, by etching openings and forming electrically conductive contact structures into the openings and/or by forming electrically conductive contact layer(s) on the substrate.
Anti-reflection structures, properties of the p-n junction, and various surface structures have been developed to optimize the general as well as application-specific performance of photodetectors. After development, the performance of prior art photodetectors, especially the sensitivity thereof, has more or less saturated. To achieve greater improvements in the detecting performance, clearly new approaches should be provided.